Japanese Patent Publication 2003-187937A discloses a test apparatus or socket for applying Burn-In Test to electronic devices such as integrated circuits and integrated circuit packages (e.g., BGA and LGA packages).
Generally, the socket includes a substrate having a number of contacts and a rectangular cover capable of moving vertically between elevated and lowered positions relative to the substrate and is forced in the elevated position by a plurality of springs mounted between the substrate and the cover. Also provided to the socket are a plurality of latching mechanisms, forcing downwardly the mounted electronic device toward the contacts to make reliable contacts between the terminals of the electronic device and the contacts of the socket. Each of the latch mechanism has a latching member pivotably mounted on the substrate and a link pivotably connected at its one end to the cover and at its opposite end to the latching member.
Referring to FIG. 15 depicting a conventional socket for testing electronic devices, the latching member 1001 has a distal end 1002 and a proximal end 1003 and is pivotably supported at its intermediate portion 1004 by the substrate 1005 so that the distal end 1002 is capable of making a contact with the upper surface of the mounted electronic device to be tested. The link 1005 includes a distal end 1006 pivotably connected to the proximal end 1003 of the latch 1001 and a proximal end 1007 pivotably connected to the cover 1008. With the illustrated arrangement, when the distal end 1002 of the latch 1001 is depressed onto the upper surface of the electronic device 1, it is subject to a reactive force F2 from resiliently supported contacts. The reactive force F2 is transformed through the link 1002 into another force F2′ which forces the cover 1008 downward. This results in that, in order to force the electronic device 1 downward by the latches 1001 for making a reliable contacts between the terminals and the corresponding contact members, the biasing force F1 from the springs provided between the substrate 1005 and the cover 1008 should be increased considerably, which in turn requires a larger initial force F0 for depressing the cover. Disadvantageously, this results in a larger deformation such as warp of the circuit board for supporting the sockets. The deformation may result in an insufficient depressing of the covers, causing defective contact between the terminals and the contact members.